Video transcript

If we were to rewind the clock
back about 70 million years, you would see dinosaurs
roaming the Earth. And this is a very nice picture
here of a dinosaur enjoying a sunset at the beach. But unfortunately
for the dinosaurs, about 65 million years ago, we
believe that a huge meteorite struck the earth and essentially
wiped out the dinosaurs. And it probably wiped out a
bunch of other species with it. Because you can
imagine, the shock wave itself would just
exterminate tons of species. Then you would have the
tsunami of unimaginable size that would just
envelop the continents for some period of time. And then you would have
all of the soot that would go into the air and maybe
make it impossible for most of the plant species
to live, because it would be blocking out
all of the sunlight. And so in an
environment like that, we could imagine that
an animal like this would be well suited to survive. It's sitting there underground. Maybe it can
hibernate in some way, so it doesn't need food
for long periods of time. Maybe it has its own food
stash under there someplace. And so we believe that our
ancient, ancient, ancient, ancient, ancient ancestors,
after this mass extinction event, might have been
something like this-- kind of a mole-looking, rodent animal
that was protected from all of this craziness that was
happening on the surface, because they like to hang
out underground and have all their food nearby them. And maybe they could
hibernate in some way. So you could imagine, once
everything settled down-- and now we're
talking, who knows, hundreds of years, thousands of
years, even millions of years-- some of this guy's descendants
start to poke their head out of the ground. And they're like, you know what? There's food in trees. And there's no one
else in the trees. And trees are a good
place to maybe get away from some of the
other predators that have managed to survive
this mass extinction event. And some of its
descendants, I should say, that were good at climbing
trees decide, hey, let's try this tree thing out. And so you started to have some
selection for the descendants of this rodent that
could climb trees well. They were able to find
food where their ancestors couldn't . They could find protection in
the trees where their ancestors couldn't. And so you could imagine that
some subset of this guy's descendants evolved
into something that might have
looked like this guy. And all the pictures
I'm showing you, these are of modern
animals, except for, of course, the dinosaur. I'm sure this was kind of
Photoshopped in some way. This is a modern bush baby. But I show this
picture because it could have been what some
of these primitive primates looked like. Because a bush baby, it
kind of a climbs trees. It kind of looks like it's
starting to get a hand here to start climbing the trees. But it also has
rodent-like qualities. But this is, of course,
a modern version of it. So this bush baby's ancient,
ancient, ancient ancestor might have been that
primitive primate or that species of
primitive primate that was a descendant of rodents
that starts to say, hey, let's see if we can climb these
trees and find some food. And then some of its
descendants might have had just the right
adaptations, found their own little niche
in the right ecosystems. And they would have
evolved into monkeys. Once again, this
is a modern monkey, but you could imagine some
type of primitive monkey. And then some of those
primitive monkeys' descendants, they turn into these
modern monkeys eventually. But some of them, they
grow larger in size. They spend more time
outside of trees. They lose their tail. They don't need it
as much for balance. Maybe it's actually
a bad thing to have, because someone
else could grab it when you're in a fight
or something like that. And they evolve into apes, and
in particular, the great apes. So one of the great apes. The great apes involve
gorillas and chimpanzees and the ancestor. Or really, the great apes
also include humanity. So let me just review
back on this timeline, just so that we
don't get confused. I'll review what we
just talked about. So before this mass
extinction event, 65 million years ago, you had
all these types of species here. Maybe this right up here. Actually, if I'm
talking about species, maybe this was
Tyrannosaurus Rex, because the dinosaurs
involve whole bunch of-- so this might
have been T Rex. And there's a bunch of species
that we could list over here. But after that mass
extinction event, that was an endpoint
for a ton of species, except for maybe this primitive
rodent mole-like thing. Maybe a lot of them
died in this event. But just enough of them survived
because they were underground or just in the
right place or they were in a mountain someplace. Who knows where they were? And some of them were able to
evolve into primitive primates. And once again, these are
pictures of primitive primates. And when I say primitive, these
are modern versions of them. So primitive doesn't necessarily
mean worse, because obviously, these guys, even
in today's world, they have a niche
for themselves. They're able to find
food and reproduce in ways that don't get in
the way of other people and the way people don't
get in the way of them. When I talk about
primitive primate, I'm just talking about kind
of an ancestral primate, maybe something that's
not there today. Although maybe some of those
descendents look very much like it. But anyway, some
of those primates evolve into primitive monkeys. Some of those primitive
monkeys' descendants become modern monkeys. So I'll call it M monkeys,
for Modern monkeys. And some of them evolve
into primitive apes. And apes, their
distinctive characteristic is that they're like monkeys,
but they don't have tails, and they're larger
than most monkeys. And so these primitive apes,
some of their descendants are modern gorillas. At some point, they break off. Some of these descendants
are an ancestor of both modern chimpanzees
and of human beings. And we think, just looking
at the DNA evidence, we think that this
departure right here-- and the
fossil evidence-- was about seven million years ago. That's our best guess for
when we, as human beings, had a common ancestor
with the chimpanzees. Now, you have that
common ancestor. Some of that common
ancestor's descendants became modern chimpanzees. And some of them-- maybe they
explored the right ecosystem, where it was more
advantageous to do so-- started to walk on two legs. And the most famous
fossil of this is the australopithicine
fossil of Lucy that was discovered
3.2 million years-- it was discovered more recently. It's 3.2 million years old. So the whole
genus-- and genus is kind of one level of
categorization above species. The whole genus of
australopithecine, these were four to two
million years ago. And we never know. You could always
find a fossil that's older than this,
maybe newer than this. I read one account that says,
maybe one million years ago. But give or take,
the Lucy fossil, which is the most
well established australopithecine fossil, is
about three million years old. And this is a reconstruction
I have over here of Lucy. So this is probably
what Lucy looked like. And once again, there
were many Lucys. It wasn't just
there was one Lucy. And we're all
descended from Lucys. And it's actually not
even clear that we're even descended directly
from australopithecine. We might be a cousin species or
a cousin genus, I should say. Genus is the category
right above species. So if you fast forward
a little bit more-- you go to about 2.3 to 1.4
million years ago-- we see fossils that
they're standing upright. The brain size is bigger. Because if you look at the
australopithecine fossils, they are standing upright. But they're cranial
capacity isn't that different than chimpanzees. You fast forward to 2.3 million
to 1.4 million years ago, we start to see fossils where
they're standing upright still. And the cranial
capacity has grown. And you're starting
to see primitive stone tools around the bone fossils. And so we believe that
these are one of the first. And this is really just
how we categorize it. But these are some of the first
fossils that we categorize as belonging to the
same genus as ours. And the genus is Homo. And Homo just means man. So it's the group right
above species of man. And we call them similar
to man, because it looks like they're starting
to make primitive stone tools. And they stand upright like us. And they have larger
cranial capacities than the australopithecine
fossils or modern chimpanzees. And once again, we don't know
if Homo habilis, which literally means-- so the Homo
part means man. Habilis means handy, because he
liked to, I guess, make tools or whatever else. We don't know if Homo habilis is
a descendant of Lucy's species of Australopithecus or
maybe a cousin species. Maybe they're both descendents
from some common ancestor. We're not quite sure. Then you fast forward
a little bit more. We're talking now about 1.8
to 1.38 million years ago. And we start seeing fossils
where the cranial capacity larger than Homo habilis,
getting closer in size to what our notion is of
kind of a modern person's cranial capacity, at least
relative to body size. And this is Homo erectus. And once again, we don't
know if Homo erectus is the descendant
of Homo habilis. Maybe they have a
common ancestor. Who knows? And it looks from
the fossil evidence that there was, especially when
you look at this range here, some overlap where you had
both Homo erectus and Homo habilis living on the same
planet at the same time. Now, you fast forward even more. And we think about 600,000
to 300,000-- once again, all of these are
constantly being modified, as we get better at
finding new fossils or interpreting
the fossils we have or we look at DNA
evidence or whatever. About 600,000 to 300,000 years
ago, the Neanderthals appear. And Neanderthals are in
the same genus as humans. So it's really Homo
neanderthalensis. I always have
trouble saying this. So this is still part of Homo. And a common misconception
is that the Neanderthals are somehow a more primitive
version of humans, that they're somehow cavemen,
and we're modern men. That's not the case. The belief is that
Neanderthals are either cousin species-- we
have a common ancestor-- or that they're actually a
sub-species of human beings. And there's some
belief that they might have interbred
with Homo sapiens. And maybe some or a good number
of us have a Neanderthal genes. And it's nothing
to be ashamed of. It's just something,
unfortunately, that Neanderthals just get a
bad name, because of, I guess, our popular culture. So this is a drawing
of a Neanderthal brain. They actually had a fairly
large cranial capacity. Although scientists, they kind
of make one reason or another why we think that
they might have been more primitive
than Homo sapiens. But who knows? We don't know. We're constantly learning
things every day. But of course, the
whole point of this is to talk about how humans
showed up on this planet. And the first
really human fossils we find about 200,000 years ago. And remember, we're
in the genus Homo. And now, we've finally found
something that looks just like us, anatomically, at least. We can't study its
behavior and all the rest. And now we get to Homo sapiens. The Homo part, once
again, means man. And the sapiens means thinking. So we can debate whether
it's an appropriate title for our species, but
it's "thinking man." So once again, the
Neanderthals, they were either a cousin species
for a lot of this time, especially once Homo
sapiens showed up. And maybe Homo sapiens
showed up before this. We just haven't found
the fossils yet. They were maybe both
inhabiting the same planet. Maybe there was
some interbreeding. But the Neanderthals disappeared
about 30,000 years ago. 30,000 years ago,
these guys disappeared. Maybe some of them
kind of got mixed in with the Homo
sapiens, started to interbreed with them. Or they might have
just been killed off, because they were fighting
over the same ecosystems. And I've made a little
sample here of Homo sapiens. Well, I'm assuming most of you
watching this video are one. But just in case,
here's my little sample. We can debate how representative
a sample of our species this really is.